EP2041226A1

EP2041226A1 - Bituminous composition, fabrication process and use thereof in road engineering

Info

Publication number: EP2041226A1
Application number: EP07787673A
Authority: EP
Inventors: Nuria Uguet Canal; Laetitia Herrero; Javier Hurtado Aznar; Didier Lesueur
Original assignee: Eurovia SA
Current assignee: Eurovia SA
Priority date: 2006-07-19
Filing date: 2007-07-18
Publication date: 2009-04-01
Anticipated expiration: 2027-07-18
Also published as: FR2903991B1; EP2041226B1; ES2570303T3; FR2903991A1; US20100206197A1; PL2041226T3; WO2008009694A1; CA2659487C; CL2007002111A1; CA2659487A1

Abstract

The invention concerns a fabrication method of a bituminous emulsion, consisting in the use of a primary bitumen emulsion, possibly diluted, characterized by a median diameter of less than 2 µm, as aqueous phase of a secondary bitumen emulsion characterized by a median diameter of more than 2 µm, wherein the final emulsion thus obtained is characterized by a bitumen content of 50% to 95% by weight, a STV viscosity at 40 C through the 4 mm orifice of less than 300 s and a settling tendency of less than 10% as determined by means of assay EN 12847.

Description

Bituminous composition, its manufacturing process and its use in road engineering

The ^invention relates to an aqueous bituminous composition for use in road building, its means of manufacture and use in road construction. The composition is obtained by dispersing a primary bitumen emulsion, characterized in that its particle size is less than 2 .mu.m in the aqueous phase used for manufacturing ^a secondary emulsion of bitumen, characterized in that its particle size is greater than 2 microns which allows to ^obtain a final emulsion of bitumen containing up ^to 95% bitumen, characterized by a low viscosity which allows its use with the present methods of implementation and transportation road bitumen emulsions.

For a better understanding of the invention, it seems useful to give the following definitions:

- Bitumen means a road bitumen or any bitumen-based composition optionally containing one or more acid or base and / or one or more emulsifiers and / or one or more viscosifiers and / or one or more fluxers and / or one or more plasticizers and / or any other additives for ^adjusting the properties of the composition, with ^the exception of polymeric additives. Road bitumens are so-called natural bitumens, derived from crude oil, oil shales, heavy oils, oil sands, etc., and obtained in particular by distillation and deasphalting of the heavy fraction resulting from the distillation. The specifications for road bitumens are described in standard NF EN 12591, "Specifications of road bitumens", but also in the draft standards prNF EN 13924 "Specifications of hard road bitumens". Is also meant bitumens modified by a polymer, ^that is to say the bitumens containing at least one polymer and more generally any bitumen-based composition containing at least one or more polymers and / or one or more acids or bases and / or one or more emulsifiers and / or one or more viscosifiers and / or one or more fluxes ^of petroleum origin, coal, plant, animal or other and / or one or more plasticizers and / or any other additive to ^adjust the properties of the composition. The specifications for modified bitumens are described in the draft standard prEN 14023, "Polymer-modified bitumen specifications". Finally and by extension, shall also include bitumen substitutes called "synthetic binders" or "clear binders", which are non-oil products to reproduce the properties, including mechanical and adhesive, bitumen ^except their black color, thereby produce materials of non-black pavement, optionally dyeable by introducing ^a pigment and / or by choosing colored aggregates;

- By polymer is meant natural or synthetic polymers. It is ^a question, for example ^a polymer of the elastomer family, synthetic or natural, and indicatively and without limitation, random copolymers, multiblock or star styrene-butadiene in any proportion or copolymers of the same chemical family (isoprene, natural rubber, ...), optionally crosslinked in situ, copolymers ^of vinyl acetate and ^ethylene in all proportions, or the same category (butyl acrylate, methyl, ... and polyolefins). It can be recovered polymers, for example from rubber crumbs obtained from used tires, various waste (cables, packaging, agricultural, ...) or any other polymer commonly used for the modification of bitumens such as those mentioned in writing Technical Guide by ^the International Road Association (PIARC) and published by the Central Laboratory of Bridges and Roads "Use of Modified Bituminous Binders, Special Bitumens and Bitumens with Additives in Road Pavements" (Paris, LCPC, 1999) as well as any mixture in any proportion of these polymers;

- by acid, is meant for example, ^phosphoric acid and its derivatives, salts and esters, ^hydrochloric acid, ^sulfuric acid, ^acetic acid and any acid or combination ^of acid,

- Mineral or organic filler means, for example, clays, mineral fines, cement, lime, silica, carbon black, mineral fibers, metallic or organic, especially textile fibers;

- Bitumen emulsion means an aqueous dispersion of bitumen optionally containing one or more additives and / or one or more emulsifiers and / or one or more viscosifiers and / or one or more fluxing agents and / or one or more plasticizers and / or any other additives for ^adjusting the properties of the ^emulsion. ^The emulsifier may be a surfactant and / or solid and / or a mixture in any proportion of these products. An emulsion is defined here as concentrated if the bitumen content is greater than 72%;

- by asphalt is meant a mixture of aggregates sorted by size and ^a bitumen optionally comprising one or more additive (s), for example, organic or inorganic fibers, rubber crumb, optionally from the recycling of used tires, miscellaneous waste (cables, polyolefins, ...) and their mixtures in all proportions;

- by aggregates we mean aggregates ^of various origin, among which the aggregates from quarry or gravel, recycling products such as aggregate from the milling ^of old asphalt, manufacturing waste, materials from recirculated building materials (demolition concrete, ...), dairy, shale, artificial aggregates of any origin and for example from bottom ash ^from incineration of household refuse (MSWI), and mixtures thereof in all proportions. Specifications for these materials are described in DIN EN 13043 regarding the "Aggregates for bituminous mixtures and surface treatments for roads, airfields and ^other trafficked areas";

- by cold mixes is meant any mixture obtained by mixing ^a bitumen emulsion and aggregates, dry or unsaturated, optionally in the presence of ^water added in addition to that of ^the emulsion and that naturally present in the aggregates, and ^additives which may be the same as those generally employed in the asphalt, as well as more specific additives designed in particular to control the breaking of ^the emulsion, such as switches that may be selected for example from acids or bases, mineral additives such as hydraulic cement (Portland cement, pozzolans, Sorel cements, ...), lime, or mineral salts as well as setting retarders which can also be mineral salts or organic compounds such as for example, acids, bases or surfactants, agents such as salts or their acid with inorganic phosphates, phosphonates and phosphinates and / or polyphosphates and / or organic. Said cold mixes may for example be obtained by mixing in various proportions an emulsion of bitumen and a wet or dry granulate. Generally, the mixture makes it possible to finally obtain between 0.1 and 30 parts by weight of bitumen per 100 parts of dry aggregate (ie 0.1-30 parts per cent of phr) and preferably between 2 and 15 phr according to the applications. Examples ^of mixes well-known cold man ^'s ^art are cast mixes cold bituminous grout, gravel-emulsion them cold dense mixes, cold-open coated, reprocessing or recycling instead of or in plant old pavements with ^the bitumen emulsion or the cold bituminous concretes;

- by surface dressing is any mixture to get the final surface layer containing embedded aggregates in asphalt thin film, as described in the Technical Guide "Superficial Coatings ^for Wear" published by the Department ^of Technical Studies roads and Motorways (SETRA) and the Central Laboratory for roads and Bridges (LCPC) in may 1995. in particular, bitumen emulsions can be used advantageously for this type of ^application.

The bitumen emulsions generally comprise between 50 and 72% by weight of bitumen that may optionally contain one or more additives and a supplement often called "aqueous phase" may optionally contain one or more emulsifiers and / or additives. The bitumen is present in ^the emulsion in the form of droplets having a particle size can be easily measured by various experimental techniques described in ^the book edited by P. Becher "Encyclopedia of emulsion technology", vol. 1 (Marcel Dekker, New York, 1983), the most widely used is probably the diffraction of light implemented by devices known as "laser granulometers" and marketed for example by the companies Malvern or Coulter. The particle size is often expressed in terms of median volume diameter, denoted d ₅ o, which represents the diameter at which 50% (by volume) of particles of ^the emulsion have a diameter larger than (or equivalently, lower) at this value. The bitumen emulsions are obtained by fragmentation of the bituminous binder in the presence of the aqueous phase in suitable devices that can be continuous, such as colloidal mills or static mixers, or batchwise, such as certain processes known as phase inversion. in concentrated mode.

The aqueous phase may also contain additives, particularly emulsifiers, bases and / or acids allowing for example ^to adjust the pH, salts, as well as viscosifier or even emulsions of bituminous non-products, such as natural or synthetic latexes. In ^the manufacturing step, the role of ^the emulsifier, which may be a mixture of different products, is to promote the formation of the bitumen droplets and stabilize them, thus enabling the survival of ^the emulsion. Although ^it is not always strictly necessary, some bitumens which can be emulsified without additives, ^the emulsifier is almost always used and is generally used in the aqueous phase, even though ^it can also be provided, wholly or partly, in the bitumen phase.

As a result, bitumen emulsions are generally characterized by the type ^of emulsifier used to keep the bitumen dispersion. Cationic emulsions are known, ^that is to say obtained with an emulsifier comprising one or more ionic groups carrying a positive electric charge. These emulsifiers generally require working in an acidified medium at pH levels that can reach in the customary and nonlimiting manner, values of 1.5 to 3. Anionic emulsions are also used, and are obtained with an emulsifying agent comprising one or more groups ( s) ionic (s) carrying a negative electric charge. This usually requires working in basic medium at pH can usually reach values of 10 to 12. There are also based emulsions ^other types ^of emulsifiers, such as nonionic and amphoteric, ^employment uncommon in road engineering. The nonionic emulsifiers do not have an ionic group and the amphoters have both cationic and anionic groups depending on the conditions. It is also known that solid particles such as clays and colloidal silica can emulsify bitumen and are therefore also considered as emulsifiers. The nature and emulsifier content to adjust the rupture velocity of ^the emulsion and ^the man of ^art knows formulate controlled rupture speed emulsions, fast, slow or intermediate, to meet the common applications. Bitumen emulsions are used routinely in road application to various applications where they are spread either alone for example, of layers ^hooking, layers of ^impregnation and spot repairs (stitch in time, seals, sealing cracks) or in the presence of aggregates to make surface coatings or so-called "cold" mixes. Typical applications of bitumen emulsions and characteristics ^that they impose on ^the emulsion can for example be found in the book edited by the Section of Manufacturers ^of emulsions Road bitumen (SFERB) of I ^'Union of Trade Unions of French Road Industry (USIRF), "Emulsions of Bitumen" (SFERB, Paris, 1988).

In all cases, ^the emulsion is a vector allowing ^to bring the bitumen, which must be stable in storage before use but whose failure ^when it is applied seeking to obtain. Break ^s' herein as the transition ^from an initial state where the bitumen is dispersed as fine droplets in an aqueous phase (emulsion) to a final state where the bitumen comprises a continuous film which may for example be coated aggregates. Thus, the bitumen emulsions have storage stability specifications, which are described, for example, in the French specification standard for cationic emulsions (NF T 65-011). According to the European standard EN 13808 gives a framework for specifying bitumen emulsions, the stability criteria should be given according ^to test EN 12847 "Determination of settling tendency of bitumen emulsions," and of measuring the difference between the water contents of the upper and lower layers of a prescribed sample volume after standing at room temperature for one week.

^The emulsion is a vector to bring the bitumen, reducing the water content used to limit the volume ^of emulsion necessary to provide the given amount of bitumen required by ^the intended application. Also, it is generally seeks to maximize the bitumen content in ^the emulsion in order to reduce transportation costs. This allows parallel reduce ^water consumption which represents an obvious interest in areas where ^water is a resource to save. Finally, rupture of ^the emulsion proceeds in part from ^water, in particular by evaporation, and, all other parameters constant moreover, a concentrated emulsion may therefore break more quickly ^that an emulsion having a lower bitumen content.

One of the essential properties ^of a bitumen emulsion is its viscosity. An excessively viscous emulsion can not be handled by equipment currently used in road engineering, particularly pumps and spray nozzles. Furthermore, in applications where ^the emulsion is used to manufacture a cold mix, too viscous emulsion could not properly coat the aggregate. Too fluid emulsion ^is not always sought either because it creates risk of runs during the spreading or ^the coating and facilitates sedimentation of bitumen drops, limiting held in storage. However, ^the use ^of bitumen emulsions to achieve ^the impregnation ^of a granular carrier requires a low viscosity allowing penetration of ^the emulsion within the support. Consequently, and according to their field of ^application envisaged, bitumen emulsions have viscosity specifications, which are described for example in French standard specification for cationic emulsions (NF T 65-011).

According to the European standard EN 13808 gives a framework for specifying bitumen emulsions, viscosity criteria must be given according ^to test EN 12846 "Determination of flow time of bitumen emulsions using viscometer flow ", commonly referred to as viscosity STV (for Standard Tar Viscometer) and of measuring the time it takes for ^the emulsion ^to flow through a standard device having a 2 port, 4 or 10 mm in diameter, at a temperature ^of test typically 25, 40 or 5O ⁰ C. the control of the viscosity of ^the emulsion is essentially obtained by the bitumen content, even ^if it exists additives having a viscosity character whose significant additional cost, however, limits ^the use industrial. Indeed, it is well known to ^those skilled in ^the art that ^a low bitumen content emulsion has a viscosity lower than that ^of an emulsion with a high bitumen content, which is described for example in the book already quoted "Emulsions of Bitumen" (SFERB, Paris, 1988).

For this reason, bitumen emulsions used today in road engineering do not exceed 72% by mass of bitumen, because ^emulsions more concentrated with the current means imply a too high viscosity that would not allow their use with commonly used materials in the industry.

However, the manufacture ^of concentrated emulsions of bitumen over 72% is possible. Thus, Patent EP 0162591 owned by BP and Intevep describes the production by a batch process ^of emulsions having between 70% and 98% bitumen. Also, Patent EP 0,999,890 belonging to CNRS discloses the manufacture by a batch process ^of emulsions having between 75% and 95% bitumen having a particle size less than 2 microns. Concentrated emulsions produced according to these methods by phase inversion under laminar flow conditions, have a pasty to conduct ^image of mayonnaise, characterized by a high apparent viscosity, as described for example in ^the article by GA Nuήez, M. Briceήo, C. Mata, Rivas, H. and Joseph DD, "Flow Charactehstics of Concentrated Emulsions of Very Viscous Water", in the Journal of Rheology (40, 3, 1996, pp. 405-423).

One way to reduce the viscosity of such emulsions is to dilute with an aqueous solution not containing bitumen, reducing the bitumen content and therefore losing ^the advantage of the high bitumen content. This dilution method is described in the patents already mentioned, as well as in EP 0 994 923 belonging to Colas which consists of diluting a concentrated emulsion continuously manufactured in a colloid mill.

In ^other words, the existing processes for manufacturing concentrated emulsions bitumen generate too viscous emulsions for use as such in road building and are therefore diluted to be employed in lower bitumen contents, losing ^the advantage of the high concentration of bitumen. ^The concentrated emulsion is thus an intermediate of manufacture.

However, it is known that the viscosity ^of an emulsion, in particular bitumen, can be reduced without modifying the bitumen content, playing on the presence of several drops of populations with different sizes.

Thus, patent GB 362 577 owned by Colas Products Limited, AG Terry, LG and Gabriel JFT Blott, describes the production by a batch process, ^of concentrated emulsions of bitumen up ^to 85% bitumen, obtained by emulsifying in a reactor in the form of coarse droplets, for example with a diameter of 20-30 μm, a bitumen within an already formed primary bitumen emulsion ^having a drop diameter of less than 2 μm. However, this process has the great disadvantage ^of being discontinuous, requiring the reactor building very large ^if one wants to get manufacturing yields ^of about 20 tonnes per hour are common values in the profession . In addition, it requires ^the gradual addition of hot bitumen (125 ⁰ C) in a primary emulsion ^containing water, thereby generating strong vapor clearances and significant overpressure requiring very demanding specific installations in terms of safety. Also, vaporization ^of part of the ^water makes the control of levels of each of the more difficult components. Finally, this process generates a population of very large particles (20 microns to 30 microns), which ^s' are very unstable on storage and generate a strong sedimentation of ^the emulsion. U.S. Patent 5,419,852 owned by Intevep SA, describes the manufacture by a continuous process, ^of concentrated emulsions of bitumen with a low viscosity containing from 70% to 85% bitumen, obtained by mixing two primary emulsions characterized in that each emulsion has a different diameter, ^one having a diameter D _L of 10 .mu.m to 40 .mu.m, and ^the other a diameter D _s of less than 5 .mu.m, and such that D _L / D _s is greater than 4 and that the mass proportion of drops of diameter D _L is between 45% and 85%. However, this method has ^the disadvantage of requiring to manufacture separately two primary concentrated emulsions of high viscosity that ^it must be transported in order to mix them. Although the transport and mixing can be carried out on the same industrial plant, the pumping systems necessary to move the primary emulsions involve major changes in the current installations such as high-pressure pumping systems requiring specific installations that are very demanding in terms of terms of security. The present invention aims to solve these problems by producing a concentrated workable bitumen emulsion without difficulty ^using means presently used for ^the manufacture of road bitumen emulsion and having good storage stability. Indeed, and surprisingly, the Applicant has discovered that ^the use ^of a primary emulsion of bitumen, characterized in that its particle size is less than 2 .mu.m, in the aqueous phase for the manufacture ^of an emulsion secondary bitumen, characterized in that its particle size is greater than 2 microns, allows to ^obtain a final emulsion of bitumen containing up ^to 95% bitumen, characterized by a STV viscosity at 4O ⁰ C with ^the orifice 4 mm less than 300 seconds and a settling tendency measured by ^the test EN 12847 below 10%, allowing its use with current methods of implementation, storage and transport of road bitumen emulsions. This final emulsion can also be diluted to adjust the bitumen content.

According to a preferred modality of the ^invention, the primary emulsion content is such that the bitumen from ^the primary emulsion is in an amount between 5% and 95% by mass of the total bitumen, and preferably between 10% and 40%.

According to a preferred modality of the ^invention, the median diameter of ^the primary emulsion is between 0.2 .mu.m and 2 .mu.m excluded and preferably between 0.5 microns and 1, 5 .mu.m.

According to a preferred modality of the ^invention, the median diameter of ^the secondary emulsion is between 2 microns and 20 microns excluded and preferably between 3 microns and 12 microns.

According to a preferred modality of the ^invention, the median diameter of ^the primary emulsion is at least 2 times smaller than that of ^the secondary emulsion, and preferably at least 3 times lower. Each of the emulsions, primary or secondary, can be manufactured by any suitable method, continuous or discontinuous, including a colloid mill, one or a succession of static mixers, by phase inversion, ... Different methods can be used for each emulsion . According to a preferred modality of the ^invention, ^the secondary emulsion is manufactured by a continuous process, for example a colloid or one or a series of static mixers mill. According to a further preferential embodiment of the ^invention, ^the primary emulsion is made by phase inversion under laminar flow conditions as described in EP 0999890 and ^the secondary emulsion is made in a colloid mill.

^The primary emulsion can be manufactured by the method according to ^the invention, so as to use a final emulsion according to ^the invention as the primary emulsion ^of a new emulsion according to ^the invention. ^The primary emulsion may be diluted beforehand, optionally with ^the aid ^of an aqueous solution containing additives such as, but not limited to, emulsifiers, acids, bases, salts, thickeners, ... The s dilution may also ^operate during the manufacture of ^the secondary emulsion, for example by directly injecting ^the primary emulsion, an aqueous solution of dilution and the bitumen ^the secondary emulsion in ^an emulsifier.

The ^invention also relates to bitumen emulsions obtained in this way, the properties of which can be easily adjusted by a judicious choice of components. According to one embodiment of the ^invention, ^the primary emulsion is carried out either with a different bitumen that of ^the secondary emulsion, or with one or more different emulsifiers or a combination of both. Bitumens may in particular differ in degree and / or the origin and / or presence ^of one or more additives making it possible ^to adjust the properties, such ^that one or more polymers, acid, plasticizer, alone or in combination.

^The primary emulsion may be made from ^a softer asphalt than the secondary bitumen, by a choice of appropriate grade and / or by ^the use ^of a plasticizer and / or a flux, in order to adjust workability and / or compactibility and / or quality ^of coating and / or the mechanical properties ^of a cold mix using the composition.

^The primary emulsion may also be made from ^a harder bitumen that the secondary bitumen, by a choice of appropriate grade and / or by ^the use ^of a plasticizer and / or a flux, in order to adjust workability and / or compactibility and / or quality ^of coating and / or the mechanical properties ^of a cold mix using the composition.

According to a preferred modality of the ^invention, the composition is characterized in that the bitumen of ^the primary emulsion is a bitumen modified by a polymer, obtained by adding 0.5% to 30% by weight of polymer derived of the family of synthetic or natural elastomer, more preferably an elastomer selected from styrene butadiene copolymers optionally crosslinked in situ, or copolymers of ^ethylene and ^vinyl acetate and / ^or methyl acrylate, and mixtures thereof ^the emulsifier of each emulsion may be selected from cationic emulsifiers, anionic, amphoteric, nonionic or mixtures thereof. The primary and secondary emulsions can be made with different emulsifiers, for ^adjusting the kinetics of disruption of ^the emulsion. In particular, they can be selected to adjust the handling and / or compactibility and / or quality ^of coating ^a cold mix using the composition. ^The emulsifier of ^the primary emulsion can also be used to emulsify the bitumen secondary, without ^the addition of additional emulsifier.

^The primary emulsion may thus be made from ^a softer bitumen but also ^a more stable emulsifier for ^the secondary emulsion, allowing, during use in cold mix, to keep a "reserve" ^of unruptured soft fine emulsion for lubrication of ^the asphalt during its implementation in particular up to compaction, and also enabling a more uniform coating.

^The primary emulsion may also be made from ^a harder bitumen but also ^a more stable emulsifier for ^the secondary emulsion, allowing, during use in cold mix, to keep a "reserve" ^of hard fine unbroken emulsion for ^obtaining improved mechanical properties for long term (several weeks).

^The primary emulsion may be formed from ^a harder bitumen but also ^a less stable emulsifier for ^the secondary emulsion, allowing, during use in cold mix, to ^obtain a first film ^emulsion fine lasts around broken aggregates for ^obtaining improved mechanical properties in the short term (a few hours).

^The primary emulsion may be made from ^a bitumen modified by one or more polymer and ^the secondary emulsion starting with ^a pure bitumen, the choice of each of the emulsifiers being performed so as to obtain during the breaking phase continues modified bitumen in which are trapped bitumen drops of ^the secondary emulsion, in order to create an elastomeric "reinforcement" within the binder film.

^Primary emulsion and the aqueous phase of ^the secondary emulsion may further contain any type ^of additive allowing ^of in controlling the properties including the viscosity-modifying agents, regulators outlet or salts, e.g., calcium chloride , potassium, sodium or any other salt of calcium, potassium, sodium or magnesium. Where ^the additive is a non-asphalt emulsion, especially an emulsion ^of a polymer, for example a synthetic rubber latex, is also considered.

According to a preferred modality of the ^invention, the content and nature of the polymer in residual binder obtained after starting ^the water from the composition, provides a durable character to fuels, notably kerosene and gasolines, for example its use in airport parking areas or service stations.

The ^invention also relates to ^the use of these particular compositions road or airport technology for the manufacture of materials for new pavements, for strengthening or maintenance of old pavements or spot repair, but also for ^the work of sealing roofs, bridges, etc. or for paints, for example, and without limitation, industrial floors. According to a preferred modality of the ^invention, the composition enters the formulation ^of a tie ^layer concentrated to rapid fracture, in particular a layer ^of said hooking "clean" residual binder which does not stick to vehicle tires site thanks to ^the hard bitumen employment.

According to a preferred modality of the ^invention, the composition enters ^the formulation of an emulsion ^of impregnation, characterized in that the small particles from ^the primary emulsion penetrate the granular carrier while the larger particles remain on the surface forming a protective layer (curing or sealing coating).

According to a preferred modality of the ^invention, the composition enters ^the formulation of a bituminous mix, e.g., a cold-cast bituminous mix, characterized by a fuel resistant nature and / or its high adhesion with ^the use of any or part of aggregates having a good coefficient of resistance to polishing, such as calcined bauxite and / or by non-black color through ^the use of clear binders optionally combined with pigments and / or aggregates chosen for their color.

According to a preferred modality of the ^invention, the composition enters ^the formulation of a bituminous mix, e.g., a cold bituminous concrete, the mechanical properties during the implementation and / or final, once ^a broken emulsion are regulated by ^employment in primary and secondary emulsions ^of various emulsifiers and / or bitumen of different grades and / or containing plasticizers or fluxes of different nature and content.

According to a preferred modality of the ^invention, the composition enters ^the formulation of a surface coating made ^of a concentrated emulsion and fast-breaking, which can optionally be characterized by its resistance to fuels, and / or its high tack with to ^the use of all or part of aggregates having a good coefficient of resistance to polishing, such as calcined bauxite and / or its non-black color through ^the use of clear binders optionally in combination with pigments and / or aggregates chosen for their color.

^The emulsion may also be used wherever concentrated bitumen emulsions are of interest, particularly in the manufacture ^of sometimes called semi-warm mix of preheating slightly (less than 100 ⁰ C) aggregates prior to kneading in the presence ^a concentrated bitumen emulsion.

^The interest and practical arrangements of the ^invention are illustrated, without limitation, by the following examples.

Comparative Example 1: Preparation ^of a primary emulsion EPO according to ^the prior art

A primary emulsion containing 62% EPO Repsol bitumen 160/220 and 0.3% ^of fatty diamine emulsifier Asfier 100 Kao, industrially obtained ^by means ^of a colloid mill in ^the Probisa plant Santiago de Compostela Spain and average particle size of 4.18 microns is used.

Example 2: Preparation ^of a primary emulsion EP1 according to ^the invention A primary emulsion EP1 (Table 1) is produced by laminar flow in phase inversion from ^a Nynas 70/100 grade bitumen ^and an aqueous phase acidified with ^the hydrochloric acid in sufficient quantity to obtain a pH of 2.5 and containing 15% ^of a cationic emulsifier, a fatty diamine (Dinoram S Ceca).

10 parts by mass of the aqueous phase, initially at 5O ⁰ C, are introduced into 100 parts of bitumen at 9O ⁰ C, placed in a heating reactor with a ^stirring system with controllable speed. ^Stirring is maintained at 600 revolutions / min for about 15 min and ^the emulsion concentrate thus obtained is diluted to a mass bitumen content of 57%.

The median diameter of ^the corresponding EP1 emulsion as measured with a laser granulometer Malvern Mastersizer 2000 of the mark is 0.5 microns.

Example 3: Preparation ^of a primary emulsion DP2 according to ^the invention

A primary emulsion DP2 (Table 1) is manufactured in colloid mill from ^a Nynas 70/100 grade bitumen ^and an aqueous phase containing 2% ^of a fatty acid amido alkyl betaine emulsifier (AGAAB) supplied by Goldschmidt, and a sufficient quantity of sodium hydroxide to obtain a pH of 12.5.

40 parts by mass of the aqueous phase, initially at 25 ⁰ C are introduced into 60 parts bitumen at 14O ⁰ C in ^a colloidal mill Emulbitume laboratory.

The median diameter of ^the corresponding EP2 emulsion, measured at the laser granulometer Mastersizer 2000 is 0.8 microns.

Example 4: Preparation ^of a primary emulsion EP3 according to ^the invention

A primary emulsion EP3 (Table 1) is produced by laminar flow in phase inversion from ^an industrial Styrelf modified bitumen 24/60, manufactured by Eurovia in ^the plant Périgueux, containing 5% of styrene-butadiene copolymer crosslinked sequence in-situ ^and an acidified aqueous phase ⁱⁿ sufficient hydrochloric acid to achieve a pH of 2.5, and containing 20% ^of a cationic emulsifier, a fatty diamine (Dinoram S Ceca).

10 parts by mass of the aqueous phase, initially at 5O ⁰ C, are introduced into 100 parts of bitumen at 9O ⁰ C, placed in a heating reactor with a ^stirring system with controllable speed. ^Stirring is maintained at

600 rpm / min for about 15 min and ^the emulsion concentrate thus obtained is diluted to a final mass bitumen content of 61%.

The median diameter of ^the corresponding PI3 emulsion, measured at the laser granulometer Mastersizer 2000 is 0.7 microns.

Comparative Example 5: Preparation ^of a final emulsion EFO according to ^the prior art

25 parts by mass of ^the primary emulsion EPO were added to 75 parts ^of a bitumen 160/220 Nynas initially at 9O ⁰ C in a heating reactor with a ^stirring system with controllable speed. ^Stirring is maintained close to 200 revolutions / min for about 3 min and ^the emulsion concentrate thus obtained is diluted with 20 parts of ^water to obtain a final content of nominal weight bitumen 75%. ^The corresponding EFO emulsion (Table 2) has a clearly bimodal granulométhe (Figure 1). Its bitumen content measured was 73%, including 17% of the total is present in the form ^of primary emulsion, by formulation. For manufacturing, ^the emulsifier used in ^the primary emulsion (fatty diamine) is also used in ^the secondary emulsion. STV viscosity at 4O ⁰ C by ^the 4 mm hole in ^the EFO emulsion is 14 s and the settling tendency (storage stability) of 18% (Table 3).

Example 6: Preparation ^of a final emulsion EF1 according to ^the invention

0.25 parts by mass ^of a cationic emulsifier, a fatty polyamine

(Polyram S Ceca) are mixed with 16.75 parts of ^water acidified ⁱⁿ hydrochloric acid in sufficient quantity to obtain a final pH of 2.5. 15 parts of ^the primary emulsion EP1 are mixed with this mixture to form 32 aqueous phase portions of ^the secondary emulsion.

32 parts by mass of this aqueous phase, initially at 25 ⁰ C are introduced into 68 parts ^of a bitumen Nynas 70/100 to 14O ⁰ C in the colloidal mill Emulbitume. ^The corresponding EF1 emulsion (Table 2) has a clearly bimodal granulométhe (Figure 1). Its bitumen content is 77%, 11% of the total is present as ^primary emulsion, by formulation. For manufacturing, ^the emulsifier used in ^the primary emulsion (fatty diamine) is different from that used in ^the secondary emulsion (fatty polyamine). STV viscosity at 4O ⁰ C by ^the 4 mm hole in ^the EF1 emulsion is 38 s and the settling tendency (storage stability) of 2% (Table 3).

Example 7: Preparation ^of a final emulsion EF2 of ^the invention

2 parts by mass of ^the emulsifier AGAAB already used for ^the emulsion

EP2, are mixed with 16 parts of ^water made basic by addition of sodium hydroxide in sufficient quantity to obtain a final pH of 12.5. 15 parts of ^the primary emulsion DP2 are mixed with this mixture to form 33 parts of aqueous phase of ^the secondary emulsion. 33 parts by mass of this aqueous phase, initially at 25 ⁰ C are introduced into 67 parts ^of a bitumen 80/100 BP to 14O ⁰ C in the colloidal mill Emulbitume.

^The corresponding EF2 emulsion (Table 2) has a clearly bimodal granulométhe (Figure 1). Its bitumen content is 76%, 12% of the total is present as ^primary emulsion, by formulation. STV viscosity at 4O ⁰ C by ^the 4 mm hole in ^the EF2 emulsion is 26 s and the settling tendency (storage stability) of 3% (Table 3).

Example 8: Preparation ^of a final emulsion EF3 according to ^the invention

5 parts ^of water acidified ⁱⁿ hydrochloric acid in sufficient quantity to obtain a final pH of 2.5 are added to 25 parts of ^the primary emulsion EP3 to form 30 parts of aqueous phase of ^the secondary emulsion. 30 parts by mass of this aqueous phase, initially at 25 ⁰ C are introduced into 70 parts ^of a bitumen Total 160/220 to 14O ⁰ C in the colloidal mill Emulbitume.

^The corresponding EF3 emulsion (Table 2) has a clearly bimodal granulométhe (Figure 1). Its bitumen content is 85%, 18% of the total is present as ^primary emulsion, by formulation. For manufacturing, the bitumen used in ^the primary emulsion is modified with a polymer as that used in ^the secondary emulsion is unmodified. In addition, their grades are different. STV viscosity at 4O ⁰ C ^by 4 mm orifice ^of EF3 emulsion is 180 s and the settling tendency (storage stability) of 1% (Table 3).

Table 1: Composition of primary emulsion (the weight percentages are given relative to ^the emulsion).

Table 2: Composition of the final emulsions according to ^the invention (the percentages by weight are given with respect to ^the final emulsion).

Table 3: Properties of the final emulsions according to ^the invention.

Claims

1. A process ^for producing a bituminous emulsion of using a primary bitumen emulsion, optionally diluted, characterized by a median diameter less than 2 microns, as the aqueous phase ^of a secondary emulsion of bitumen, characterized by an upper median diameter 2 .mu.m, ^the final emulsion obtained is characterized by a bitumen content of 50% to 95% by mass, a STV viscosity at 4O ⁰ C through ^the hole of 4 mm lower than 300 s and a settling tendency measured by ^the test EN 12847 below 10%.

2. A method according to claim 1 characterized in that the ratio of the median diameter of ^the secondary emulsion to that of ^the primary emulsion is greater than 2, and preferably greater than 3.

3. Method according ^to one or ^other of Claims 1 to 2 characterized in that the median diameter of ^the primary emulsion is between 0.2 .mu.m and 2 .mu.m excluded and preferably between 0.5 microns and 1, 5 .mu.m.

4. Method according ^to one or ^other of claims 1 to 3 characterized in that the median diameter of ^the secondary emulsion is between 2 microns and 20 microns excluded and preferably between 3 microns and 12 microns.

5. Method according ^to one or ^other of claims 1 to 4 characterized in that the bitumen content resulting from ^the primary emulsion is between 5% and 95% and preferably between 10% and 40% of the total bitumen.

6. Method according ^to one or ^other of claims 1 to 5 characterized in that ^the primary emulsion is obtained by phase inversion under laminar conditions and ^the secondary emulsion is obtained through a colloid mill.

7. Method according ^to one or other ^of claims 1 to 6 characterized in that the bitumen used in ^the primary emulsion differs in degree, the origin and / or ^the presence of additives used in ^the emulsion secondary.

8. Method according ^to one or ^the other of claims 1 to 7, characterized in that the bitumen constituting ^the primary emulsion is a bitumen modified by a polymer and that of ^the secondary emulsion contains no polymer.

9. The method of claim 8, characterized in that the bitumen modified by a polymer constituting ^the primary emulsion is obtained by adding from 0.5% to 30% based on the bitumen ^of elastomers selected from block or random copolymers of styrene and butadiene, optionally crosslinked situ, or copolymers of ^ethylene ^and vinyl acetate or ^a methyl acrylate or butyl acrylate, and mixtures thereof.

10. Method according ^to one or ^the other of claims 1 to 9, characterized in that the emulsifier (s) (s) used for making ^the primary emulsion is (are) used (s) without additional input of ^emulsifier for manufacturing ^the secondary emulsion.

11. Method according ^to one or ^the other of claims 1 to 9, characterized in that the emulsifier (s) (s) used for making ^the primary emulsion is (are) other (s) one (or those) used to manufacture ^the secondary emulsion.

12. aqueous bituminous composition obtained by implementation of a method according ^to one or ^the other of claims 1 to 11.

13. Use of a composition according to claim 12 in road engineering or sealing.

14. Use of a composition according to claim 12 for the production of surface dressings, cold mixes, layers ^of attachment or ^{impregnation.}

15. A bituminous mix comprising a composition according to claim 12.